A prospective study of role of MRI evaluation in knee injuries in a tertiary care hospital

Abstract

Introduction: Knee is one of the largest and most complex joints in the body. Disease processes and injuries that disrupt ligaments, menisci, articular cartilage and other structures of the knee cause painful knee resulting in significant morbidity and disability. Number of imaging modalities are currently used to evaluate knee abnormalities including standard radiography, scintigraphy, Computed Tomography (CT), planar tomography and arthrography. Materials and Methods: This study was a prospective, diagnostic descriptive study conducted in the Department of Radiology and Imaging Sciences, Tagore Medical College and Hospital, Rathinamangalam, Melakottaiyur, Chennai, Tamil Nadu. This study was conducted between January 2019 to December 2019. 100 patients presenting with knee injury referred from OPD (outpatient Department) & IPD (inpatient Department) of Department of Radiology and Imaging Sciences for MR imaging were included in the study, Arthroscopy was done in 39 patients and findings of arthroscopy were correlated with MRI findings. Sensitivity, specificity NPV, PPV and accuracy of MRI were calculated. Results: MR diagnosis of 100 cases was as follows: in ACL tear 50%; PCL tear 19%; MCL tear 17%; LCL tear 16%; MM tear 49%; LM tear 31%; Sensitivity, specificity, NPV, PPV and accuracy of MRI in detecting the knee injuries taking arthroscopy as gold standard are as follows ACL- 100%, 90.9%, 100%, 96.5% and 97.4 %; lateral meniscus-100%, 94.5%, 100%, 50% and 94.8%; medial meniscus 90.4%, 66.7%, 85.7%, 76% and 79.5% respectively. Correlation between MRI and arthroscopic findings regarding presence and absence of posterior cruciate ligament tear was highest with sensitivity -100%, specificity- 94.5%, NPV- 100% and accuracy-94.8%, There were 6 false positives for meniscus tear on MR examinations accounting for low positive predictive value (72%) of MR examination. Posterior horn tears of menisci are likely to be missed on arthroscopy. Out of 6 false positive cases of meniscus tear, 4 were located predominately in the posterior horn and 2 in the anterior horn. Thus, acceptance of MRI findings as false positive is controversial. Conclusion: MRI is a useful non-invasive modality having high diagnostic accuracy, sensitivity and negative predictive value making it a very reliable screening test for diagnosis of internal derangements of knee joint. Thus, MRI saves many knees from unnecessary arthroscopies.